The present invention pertains to methods and apparatuses for providing fluid control for fluid-handling rotary machinery, and more particularly, to apparatuses such as turboexpanders and compressors. Such apparatuses, typically, include a rotor having a series of fluid passageways therethrough, each passageway having one end open radially outwardly of the rotor. A stator, generally, surrounds the rotor and supports a number of nozzles communicating with the radially openings of the rotor passageways. Such nozzles are commonly provided on turboexpanders for injecting fluids into such rotor passageways. The nozzles, typically, are defined by a number of blades pivotally mounted on the stator. In order to provide for adjustment of the blade angle, and to close the opening between the blades, a clamping ring is, typically, provided for adjusting the blades. Frequently, the clamping ring is connected to the blades by a cam mechanism such as pin and slot arrangements, so that, upon rotation of the clamping ring, the angle of the blades can be varied.
It is desirable, in order to improve the efficiency of such apparatuses, that the fluid flow only in the channels or passageways between the nozzles. Fluid which flows outside such channels is called leakage. The greater the leakage the less efficient is the apparatus. Leakage in such apparatus, typically, occurs between the blades and the stator, and between the blades and the clamping ring or blade adjusting ring.
Accordingly, some prior art devices have utilized the pressure differential between the inlet and outlet to the device to urge the clamping ring against the nozzle blades to prevent leakage. Indentations or grooves in the nozzle blades and/or clamping ring have been used in such prior art devices to relieve, to some extent, the force on the clamping ring against the blades in order to facilitate the movement or adjustment of the blades.
It has been found, however, that such prior art devices are not capable of preventing leakage over a wide variety of flows and/or pressures of the fluid. It has also been found that such prior art devices are not capable of smooth adjustment, or fine tuning, or jar-free movement of the blades over a wide range of flow and/or pressure of the fluid.
Furthermore, and even more importantly, in many prior art devices the efficiency of such device is only relatively high for a very narrow range of operating conditions, i.e. flow rate and/or pressure. As such apparatuses are adjusted for fluid conditions which lie outside such narrow ranges, the efficiency of such apparatuses decrease drastically. This is, typically, a result of the pivotal movement of the blades to accomodate for the change in fluid flow conditions. In particular, the pivotal movement of the blades, typically, prevents the blade from presenting an optimum discharging angle or entry angle to or from the nozzle as the case may be. For example, in a turboexpander, such pivotal movements of the blade frequently alters the angle into-the-rotor in such a manner that the operating efficiency of the turboexpander is greatly reduced. This loss of efficiency is in addition to any additional loss of efficiency due to leakage.
There is a need therefore, for a flow control apparatus for fluid-handling rotary machinery which prevents or substantially minimizes the leakage of fluid around the nozzle blades of such devices over a wide range of flow rates and/or pressures. There is also a need for a flow control apparatus which is capable of maintaining a highly efficient nozzle configuration over a wide range of fluid flow rates and/or pressures.
Various embodiments of the present invention are designed to overcome many of the disadvantages found in the prior art devices.